Switch to using PBKDF2 with SHA256 (#120)
Switch to using PBKDF2 with SHA256 (#120)

* Switch to using PBKDF2 with SHA256

* Generate salt and convert some data to bytes

* Reorder imports and small change to text

* 128-bit salt, not 128-byte

* Keep password as string in SetSuperSecureCookie and convert when needed

* Rename password to secret

* Remove redundant type specifier

go-macaron/macaron,go-macaron/macaron